Recently, small-sized mobile terminals with a GPS function, typified by mobile phones, have been extensively developed. These mobile terminals have such applications as navigating pedestrians in collaboration with the GPS system, the distribution of maps via a mobile phone network, and a display application.
The positioning utilizing GPS, however, has a problem of hindering the positioning or decreasing accuracy in locations where the GPS signals are very weak as inside buildings or where the sufficient number of supplementary satellites cannot be secured as around buildings.
As for current pedestrian navigation, outdoor services are the mainstream. However, indoor services as in department stores or underground shopping arcade have been desired earnestly, and a lot of indoor positioning systems using IC tags, infrared rays, radio waves and ultrasonic waves have been researched. Any of these indoor positioning systems, however, require developing an infrastructure, which demands considerable cost and time.
The mobile terminals capable of carrying out pedestrian navigation include those that have a geomagnetic sensor for matching the pedestrian traveling direction with the display of a map. In addition, there are mobile terminals that further include an acceleration sensor for detecting the attitude of the mobile terminals (to find an azimuth in a given attitude, it is essential to detect the attitude with the acceleration sensor).
If autonomous navigation is realized by making use of the geomagnetic sensor and acceleration sensor which have already been employed by the pedestrian navigation system, the navigation inside the building or the like will become possible without developing basic technology or without loading the mobile terminal with a new component.
The autonomous navigation using the geomagnetic sensor and acceleration sensor is disclosed in Patent Documents 1-3.
Patent Document 1 relates to a portable position detecting apparatus that improves the position detecting accuracy of a pedestrian by the autonomous navigation (a configuration including sensors for carrying out detection of the number of steps×stride, correction of the stride and detection of the moving direction) capable of detecting the moving azimuth of the pedestrian more accurately even though the GPS signals cannot be received, and adjusting the stride in accordance with the walking state. The portable position detecting apparatus detects the moving position by the calculation of “the number of steps”×stride using a pedometer; corrects the stride in accordance with the walking state obtained from the walking time per step detected by the acceleration sensor; and detects the moving direction using the geomagnetic sensor, thereby improving the accuracy of detecting the pedestrian moving position by the autonomous navigation. In this way, it enables detecting the position of the pedestrian carrying the portable position detecting apparatus at an accuracy sufficient for practical applications with increasing the accuracy of the stride even in the case where the pedestrian is in a forest or in a valley between high-rise buildings where the GPS satellite signals cannot be received.
The Patent Document 2 relates to a walking navigation system for measuring the walking navigation of a pedestrian moving inside or outside the building. The walking navigation system has a computer. An input device, which is connected to the computer and worn on the waist of the pedestrian, has a forward accelerometer and an upward accelerometer detect the forward and upward accelerations while the pedestrian is walking. A CPU in the computer calculates a cross-correlation function from the detection results, compares it with cross-correlation functions about horizontal walking, upward walking and downward walking, which are stored in a hard disk (HD) in advance, and decides one of the walking modes. In this way, it enables recognizing that the pedestrian is walking on a path with a low difference of altitude such as going up and down the stairs.
The Patent Document 3 relates to a walking direction detecting apparatus for detecting the traveling direction of a mobile unit due to walking. It calculates the variation of the acceleration component in the horizontal direction between the time when the variation of the acceleration component in the vertical direction takes the local maximum and the time when it takes the local minimum; and estimates the walking direction from the direction of the acceleration component in the horizontal direction when the variation of the acceleration component in the horizontal direction takes the local maximum.
However, the apparatuses disclosed in the foregoing Patent Documents 1 to 3 impose on a user certain restrictions such as using the mobile terminal in the condition of wearing on the waist in a prescribed attitude, or demanding calibration after wearing even though the attitude is not limited, which are not user-friendly at all.
In addition, the apparatuses disclosed in the foregoing Patent Document 3 select one of the acceleration measurement values obtained during a specified period to be used for estimating the walking direction. However, in the acceleration measurement values, noise components having nothing to do with the walking movement are easy to get mixed, and this makes it difficult to estimate the walking direction at high accuracy. As an example of the noise, the slightest contact between the sensor system and pedestrian clothing brings about measurements of large pulse-like acceleration.
Thus it is desired to enable the pedestrian navigation that allows flexible wearing of the mobile terminal during the navigation, and does not impose a stress on the pedestrian (user).
The present invention is implemented to solve the foregoing problems. Therefore it is an object of the present invention to provide a traveling direction measuring apparatus and traveling direction measuring method capable of being used as the pedestrian navigation system at locations where it is difficult to obtain high positioning accuracy as inside buildings or around multistory buildings in which GPS is not applicable.
Patent Document 1: Japanese Patent Laid-open No. 2000-97722;
Patent Document 2: Japanese Patent Laid-open No. 2002-139340; and
Patent Document 3: Japanese Patent Laid-open No. 2003-302419.